Background: Small follicular cysts are commonly found in the ovaries of prepubertal girls, and in most cases, they are of no clinical importance. These cysts are usually self-limiting and resolve spontaneously. However, occasionally, these cysts may enlarge and continue to produce estrogen, resulting in signs of sexual precocity. Here, we report a case of precocious pseudopuberty associated with an autonomous ovarian follicular cyst. Case presentation: A 5.9-year-old girl initially presented to a local clinic with vaginal bleeding and a large unilateral ovarian cyst. At 6 months after the initial acute episode, the patient visited our hospital as the ovarian cyst had persisted and increased in size. Endocrinological examination showed elevated estrogen levels and suppressed gonadotropin levels on GnRH stimulation test. Also, no skin pigmentation or bone anomaly was noted. Based on these observations, laparoscopic cystectomy was performed, and histologic analysis confirmed the diagnosis of a follicular cyst. After the laparoscopic cystectomy, the patient’s hormone levels returned to normal and no ovarian cyst was detected by ultrasound. Conclusions: As autonomous ovarian cysts are usually self-limiting disorder, no treatment is necessary. Therefore, surgical management should be deferred as long as possible to avoid the risk of repeat surgery, as pseudoprecocious puberty due to autonomous ovarian cysts can resolve spontaneoulsy and frequently recurs. Precocious pseudopuberty with an ovarian cyst may be due to granulosa cell tumor or may be one symptom of the McCune-Albright Syndrome (MAS). A careful longer-term follow up of patients with autonomous ovarian cysts and/or molecular studies may be necessary in such cases.